MR2 Radiator/airflow mods

[Malcolm]

if you're wondering why, read this thread, where I outlined the reasons for doing this....
http://twobrutal.co.uk/TBforum/showthread.php?t=1068

anyway, I started work on the radiator relocation today. the radiator I'm using is an SW20 turbo one, it's practically identical to the aw11 one, with a couple of minor differences on the end tanks

First thing I did was to cut off the old, damaged radiator support beam. I don't think this is going to affect chassis strength at all, as I don't feel this is a structural member. Anyway, , before:
(click to enlarge)

after (weight reduction stage one )


then I test fitted the radiator and cut a nice big hole in the panel behind. I was going to use the original twin fans but decided they were overkill - there will be plenty of airflow when the car is moving, and a single fan is plenty to keep it cool while idling/driving slowly. This single fan is much lighter and should allow much better airflow when the car is moving
(weight reduction stage 2 )


You might think the hole is small, compared to the size of the radiator, but remember the radiator has a lot of tubes and fins, so the cross sectional area available for flow will be much smaller than the radiator itself. Also this hole is about the same size as the opening in the front bumper.

anyway the next step was to cut a slot into the bumper support beam to allow it to fit on. This also supports this end of the radiator. I was going to put a panel inside the slot with the round rubber supports that the bottom "pins" on the radiator normal go into, but I might just surround the whole thing with some dense foam rubber to hold it.

Beam (weight reduction stage 3 )


Beam installed:


next I test fitted the water to air radiator, to see where it can go. I think here should work very well, and it shouldn't pick up any heat from the much hotter radiator above like this either


I was going to relocate the bonnet latch, but I test fitted the panel and realised it could still fit quite easily. I just had to trim the bottom tab off the latch and some of the plastic grille off the fan (weight reduction stage 4 )



next I need to work on ducting, and the bonnet vents, which is going to involve making a fibreglass bonnet, which should be an interesting experience.

[RomanV]

Yes, this is an interesting topic.
Did you ever see this thread?

viewtopic.php?t=31526

Im planning on doing similar one day, once everything else is out of the way. Its why I bought that bonnet from you a while ago, but it seemed that Adam needed it more than me. Adam you can pay me for the bonnet when you bring my books back *cough*

Its an interesting idea though, Good luck, cant wait to hear how it will turn out.

Im loving that top down AW11 sketch too! That looks pretty cool.

[RomanV]

One thing that DID concern me, after giving this a lot of thought a while back, was exactly where to vent the air. To vent the air close to the radiator, you would need to have a very steep angle duct, which would shoot the air up almost vertically, which could perhaps create undesirable turbulence over the rest of the vehicle.
If you position the vent hole further back however, you meet the high pressure zone that already exists in front of the windsheild.
(Another idea that I had was to make a ski-jump at the back of the bonnet, so the window wipers would be hidden from the air flow, and ease the transition to the windsheild.. might look ugly though. )

The area just in front of the windscreen is a high pressure area... it isnt ideal venting air here, it is probably a whole lot better than under the car though.

I have a (rather dusty!) F50 model that I draw inspiration from sometimes, and it is interesting to see how the venting works on this. (Lotus elise, GT40 etc. are similar)




The air would flow around the sides of the cabin, onto the 'wide body' kind of bits, and out under the wing at the rear.

The problem I see for venting the air around the car with an AW11 or an SW20, is that the side mirrors are EXACTLY in the new path of the air flow... As you can see on the F50, they are positioned with the intent of being out of the way of this air flow.
In a worst case scenario, the bulk of airflow would travel UNDER the wing mirrors, generating lift.
Wing mirrors are responsible for quite a lot of turbulence/drag as it is, even on standard street cars.
If you go for the side vent idea, wing mirrors will be something you might want to think about.

Several of the JGTC SW20s run a single vent in front of the wind sheild, so it cant be too bad of an idea I suppose.

EDIT:

I just had another thought.

If you were clever about it, you could vent the extra air to feed the side vents of the engine bay... As these are a lot higher up on the AW11 than the SW20.
Although how hot is the air exiting the radiator? Might not be such a good thing.


EDIT 2:

I found that pic of the JGTC car.

[Malcolm]

well as you can see from the wicked picture I drew on the other thread, I want to vent it out toward the sides of the bonnet. I hadn't really thought about the wing mirrors, but it's a very valid point. There's a picture of an aw11 with little bits of string all over it in a wind tunnel, and the air runs almost vertical over about a foot of the door because of the wing mirrors. Someone suggested to me that venting straight over the roof would cause the entire car to act somewhat like an aeroplane wing and cause lift, but like you said quite a few race cars do that, so maybe it's not so bad? For now I think I'm going to do it pretty much as I showed in that drawing, but if I ever do a widebody kit for it I may duct it through the bonnet and out the front guards where there would be a gap where wide guard meets door (like on Adam's kit)

venting to the side intakes would be very difficult I'd imagine. Even if there was one on both sides (and there isn't ) simply aiming the air there would be hugely difficult.

I can't think of any good solutions for the wing mirrors, except maybe for sticking them on the front guards

[RomanV]

Yeah, Im not too sure what you could do about the wing mirrors.

Positioning them slightly lower down might be the way to go, so all of the air flows over the top.
But it would be hard to change them too much without making the car look weird.

[CozmoNz]

The following is a bit of info on the border radiator reloaction kit:




(warning bigish pix, 300kb each)

Start of Article

Taking Everything off the SW20

More Installing

Finishing up and Painting

Done and Testing

Maybe someone who understands the lang can translate the "end result table" ?

[Mr Revhead]

hmm interesting...

more air over the roof wont create lift....

i reckon if your serious about this, copy more closely what they do for sports racers etc..... mount the radiator more like youv got the i/c there.... so air goes in the grille, and up trough the rad and out the top. but not at such an angle
cut out the panel behind the rad, youd need to reinforce that and get certs etc. to me its that panel there that would cause the most drag.... espeicially as it seems to be shaped to flow air both up and down...
cutting that out and directing all the air over the bonnet would be better imo.

also very good point on the mirrors. time for some bling carbon fibre single seater types maybe?

that is a valid point in that other thread about the CoG, but as to how much real effect it has on a road car is another matter....

ill be watching with interest as its something id really like to do to mine one day

[Mr Revhead]

oh and the little air dam infront of the bonnet vent is to create a low pressure area in the opening to help suck the air out

[RomanV]

Yeah I went and talked the local certifier a while back, about cutting through to the frunk. He said that I would definitely need certification. And the hot radiator air has to be sealed away from thr brake booster, battery, etc.
And bracing around the opening of the hole would be required too.

Something to keep in mind before you cut any holes in the... woops, too late!

[Mr Revhead]

yeah, youd need to make a duct and seal it to the bonnet. but i really dont see it being a major impossible job.

[RomanV]

Definitely not... Just something to keep in mind.

I doubt you'd have room for a spare wheel anymore though, assuming you carry one anyway.

Ive been thinking about doing this, and getting it certed at the same time as my brakes/engine, you may as well get as many things certed at once as you can.

So I might have to get some bucket seats etc. too, to get value for money from my cert.

[fivebob]

more air over the roof wont create lift....

It would create lift if it accelerates the air flowing over the car, although where exactly it would act, if it occurs, is debatable. My guess is that it create a lower Cp towards the rear of the car and possibly shift the centre of pressure further forward, but that's just a guess.

[Mr Revhead]

my spare moved to the passenger footwell when i put my battery in the frunk....

[fivebob]

And the hot radiator air has to be sealed away from thr brake booster, battery,

Why? No front engined cars have to do this and look where the brake booster is on most front engine transverse mount cars

[RomanV]

Exactly what I was thinking.

Although it would be ideal to have it sealed off anyway.

[Mr Revhead]

It would create lift if it accelerates the air flowing over the car, although where exactly it would act, if it occurs, is debatable. My guess is that it create a lower Cp towards the rear of the car and possibly shift the centre of pressure further forward, but that's just a guess.

ok.... wasnt aware of that, but i think i see how when i think about it.
but would it accelerate the air?

as long as it doesnt move it around with the effects like the CLK GTR

[RomanV]

Yes the air accellerates, because it has to take 'the long way around' over the top of the car, instead of 'straight through'.

To travel a longer distance in the same amount of time requires an increased speed.

[Mr Revhead]

yes yes im aware of that.... what i mean is would the amount of air venting through there be enough to have an effect? would it accelerate it by much?

looking at an aw11 i think it wouldnt be the easiest to direct the flow around the sides....

[RomanV]

I agree, I think that over the top would be the best option.

Although one thing that I have thought of before...
Perhaps the front end lift at high speed was intentional?
Imagine going 200kph, and the nose of the car is stuck like glue... and the first thing to lose traction around a corner was the rear.

Time for a big $&#$% off triple layer carbon fibre GT wing at the back.

Or maybe routing the exhaust out the top of the bonnet, (:lol:) and making a mean venturi for the bottom of the car.

[Mr Revhead]

a slight tangent....

i noticed the vents on the s/c engine lid face forwards....
not rear like youd think.... i spose the rear window angle and the deflector creates a wicked low pressure area in there.
so how much downforce do you guys think the stock wing makes?

and at about 140kmh theres enough air pressure under the lid to hold it up on a 30deg angle....